Physical properties of starch of Asian-adaptedpotato varietiesZenaida N Ganga1 and Harold Corke2*1NPRCRTC, Benguet State University, La Trinidad, Benguet, 2601 Philippines2Cereal Science Laboratory, Department of Botany, University of Hong Kong, Pokfulam Road, Hong Kong

Abstract: Starch was puri®ed from 24 potato (Solanum tuberosum L) genotypes (varieties and

breeding selections) intended for production in Philippine conditions. Genotypes varied widely in their

thermal, pasting and other physicochemical properties. The locally bred Philippine varieties and

selected advanced clones had comparable starch qualities to the more widely grown commercial

varieties from Europe and the USA. The genotypes B71-240.2, LBR 1±5, and the three TPS hybrids

(Serrana�LT-7, HPS 7/67 and HPS II/67) had some starch properties that could make them suitable

for processing and starch production. Other genotypes have unique properties that could be useful for

industrial or other purposes. The addition of 10g litreÿ1 NaCl solution signi®cantly decreased and

stabilized starch pasting values of all the potato genotypes, but genotypes varied in their relative

response to 10g litreÿ1 NaCl.

# 1999 Society of Chemical Industry

Keywords: starch; potato; processing quality; Solanum tuberosum; thermal properties; pasting properties; texture

INTRODUCTIONPotato (Solanum tuberosum L) production has signi®-

cantly increased in recent years in many developing

countries, particularly in Asia where it has became

more important as a food and industrial crop. One of

the major reasons for this is the opening up and

expansion of markets for processed potatoes,1 as a

result of changing lifestyles and eating habits including

development of the fast food sector and production of

varied snack items. The potential for processed potato

is great, and several multinational and local companies

have already established processing plants in some

Asian countries. There is also interest in producing

starch from the large amounts of trim waste and reject

potatoes from these processing plants.

Potato starch is preferred over other starches in

many food, adhesive and oil-®eld applications as well

as in papermaking because it can give high consistency

on pasting, and it excels in ®lm-forming and binding

characteristics, with these properties also carried

through to its derivatives.2 In East Asia, there is great

potential for use of potato in the manufacture of starch

noodles. Previous reports showed that some potato

starch noodles are superior to or comparable with

other types of starch noodle (eg mung bean, rice or

sweetpotato). In many cases, potato is preferred over

corn and cereal starches for its neutral taste, and

higher noodle transparency and ¯exibility.3 Potato

starch is also used as stabilizer or as a binder in the

production of wheat-¯our-based instant noodles,4 or

as a texturizer to improve the eating quality of wheat

noodles, a common practice in Japan.5

One of the limiting factors in potato production in

these Asian areas is the lack of appropriate processing

varieties that meet the standards for the speci®c

industry uses since most of the varieties grown in Asia

are table or cooking types for the fresh market. The

objective of this study was to evaluate the starch

properties of diverse potato genotypes grown in the

Philippines including introduced varieties and selected

advanced clones, and thus to be able to identify

varieties that are suitable for processing and/or starch

production.

MATERIALS AND METHODSGermplasmThree sets of potato genotypes either introduced or

commercially grown in the Philippines were evaluated

(Table 1). Set A and set B consisted of introduced

commercial varieties from the Netherlands and the

USA, respectively. Set C are varieties and TPS hybrid

selections introduced through the International Potato

Center (CIP), Lima, Peru, and have been selected and

recommended in the Philippines. The entries I-1035

and LBR 1±5 (locally known as Montanosa and BSU

Po-3, respectively) and B71-240.2 are recommended

highland varieties which are resistant to late blight

Journal of the Science of Food and Agriculture J Sci Food Agric 79:1642±1646 (1999)

* Correspondence to: H. Corke, Cereal Science Laboratory, Department of Botany, The University of Hong Kong, Pokfulam Road, HongKongE-mail: harold@hku.hk(Received 23 April 1998; revised version received 22 December 1998; accepted 6 May)

# 1999 Society of Chemical Industry. J Sci Food Agric 0022±5142/99/$17.50 1642

(Phytophthora infestans Mont de Bary); while the clone

385130.8 is heat-tolerant and was selected for lowland

potato production areas. The clone B71-240.2, locally

known as Dalisay in the Philippines, is also a

recommended variety widely grown in China. The

variety Granola, a cooking-type potato from Germany,

is the most popular variety in the Philippines. The true

potato seed (TPS) hybrids, HPS 7/67, and HPS II/67

are from India while Serrana � LT-7 was bred at CIP.

The ®rst two hybrids are also being grown/promoted

in Vietnam, Sri Lanka and Indonesia.

Starch extraction and purificationPotato starch was extracted following Kim et al6

(1995) with a few modi®cations. This method

provides a high yield of clean starch with little loss.

Tubers were thoroughly washed, peeled and cut into

2±3-cm cubes. A 400-g batch was macerated at low

speed using a Kenwood Table Mixer (Major 250

Model) (Kenwood, England) with 400ml distilled

water for 45s and the mixture was left to stand for

20min. The liquid was decanted and the remaining

solids were macerated for another 45s. The mixture

was added back to the sediment and held at room

temperature for 40min. The liquid was decanted and

discarded, and a further 500ml of water was added to

the sediment before sieving with a 250-mm sieve. The

remaining sediment in the sieve was washed off with

200ml water and resuspended with 400ml water; after

which it was macerated for 45s and sieved (250-mm

sieve). The starch in the ®ltrate and the rinse water

were allowed to settle for 30 to 45min and the liquid

decanted and discarded. The starch was resuspended

in a litre of water and passed through a 250-mm sieve.

The remaining solids on the sieve were rinsed with

another litre of water before they were discarded. The

starch in the ®ltrate and the rinse water was allowed to

settle for 30 to 45min and the liquid decanted and

discarded. The starch was dried in a convection oven

at 35°C for two days and then ground with a mortar

and pestle and passed through a 250-mm sieve.

Samples were stored in air-tight containers at room

temperature until use.

Amylose content, swelling volume and solubilityDuplicate starch samples were analysed for amylose

content following an iodine-binding spectrophoto-

metric procedure;7 swelling volume was done follow-

ing Crosbie8 using 200mg of starch instead of the

standard 350mg; and solubility was expressed as the

Table 1. Amylose content, solubility,swelling volume, and thermalproperties of starch of 24 potatogenotypes

Genotype

Amylose

(%)

Solubility

(%)

Swelling

(mlgÿ1) To (°C) Tp (°C) Tc (°C) DH Jgÿ1

Set A

Baraka 25.7 7.5 45.3 62.9 68.0 77.6 15.3

Bimonda 24.1 6.6 42.9 66.2 71.8 83.1 15.2

Columbus 22.6 7.3 47.4 61.9 68.0 78.0 16.2

Diamant 22.3 7.7 45.9 61.5 67.5 77.4 14.8

Donald 27.6 7.3 45.3 62.8 68.4 78.4 15.5

Hertha 21.8 7.6 43.5 62.6 69.2 78.6 15.5

Remarka 20.1 7.6 44.1 63.8 68.6 76.9 13.5

Serenade 29.9 7.6 45.9 64.1 68.7 77.9 14.7

Signal 24.9 7.8 45.6 63.4 68.5 77.7 14.3

Van Gogh 34.5 7.7 44.4 65.2 71.1 81.0 14.7

Set B

Russet

Burbank

35.1 8.1 47.5 61.5 66.6 77.5 15.0

Chipetah 32.8 7.9 46.5 62.2 68.0 78.3 14.8

Granchip 32.3 8.1 48.6 62.1 68.1 69.6 13.7

Itasca 33.1 7.5 44.4 62.5 67.3 69.9 13.7

Norchip 31.2 8.1 49.3 59.6 65.4 75.2 14.4

Shepody 29.8 8.2 42.9 62.3 67.9 77.9 15.0

Set C

B71-240.2 32.9 7.8 47.8 63.9 68.4 77.9 15.5

I-1035 33.4 7.6 48.0 60.1 65.4 75.2 14.8

Ser � LT-7 22.9 7.7 41.6 66.0 71.5 82.2 15.0

HPS 7/67 26.8 8.0 43.8 67.2 70.8 80.9 14.6

HPS II/67 27.8 8.4 44.2 64.8 69.7 79.2 16.0

385130.8 31.8 8.4 42.7 63.2 69.0 78.3 14.6

LBR 1±5 32.9 7.9 45.3 61.8 66.4 76.2 14.2

Granola 34.3 7.7 45.4 61.4 67.7 77.2 14.2

Mean 28.7 7.8 45.3 63.1 68.4 77.7 14.9

SD 4.6 0.38 2.01 1.9 2.6 3.1 0.8

J Sci Food Agric 79:1642±1646 (1999) 1643

Quality of potato starch

amount of starch leached out into the supernatant in

the swelling volume test.

Starch thermal propertiesThe gelatinization properties of triplicate samples of

the different potato starch genotypes were determined

using a Mettler DSC-20 Differential Scanning Calori-

meter (Mettler-Toledo AG Instruments, Naenikon-

Uster, Switzerland) equipped with a Mettler TC11

data analysis station. Starch samples (2±3mg dwb)

were placed in aluminum crucibles and distilled water

was added to make a 1:3 (w:w, dwb) starch:water

mixture. The crucible was hermetically sealed and

allowed to equilibrate for about 1h before analysis. An

empty aluminum crucible was used as a reference. The

sample was heated from 30°C to 120°C at a heating

rate of 10°C minÿ1. The gelatinization temperature

parameters in°C of To±onset, Tp±peak, Tc±conclu-

sion and enthalpy (DH, Jgÿ1) were determined.

Starch pasting propertiesThe pasting properties of starch samples were deter-

mined using a Rapid Visco-Analyzer Model 3D (RVA)

(Newport Scienti®c Pty Ltd Warriewood, Australia).

A suspension of 2gm starch in 25g accurately weighed

distilled water or 10g litreÿ1 NaCl solution was

subjected to a 13-min continuous controlled heating

and cooling cycle (see Fig 1) under constant shear.

The peak viscosity (peak), holding or hot paste

viscosity (HPV), and ®nal or cool paste viscosity

(CPV) (Fig 1) were recorded. Stability ratio was

calculated as HPV/peak. Duplicate tests were done for

each starch sample.

Starch texture analysisAfter the Rapid Visco-Analyzer (RVA) test the starch

pastes were kept at room temperature for 3±4h then

evaluated for their gel texture properties using a

Texture Analyzer TA.XT2 (Stable Micro Systems,

Godalming, England). A cylindrical ¯at-ended 5-mm

probe was used in a standard two-cycle program at a

testing speed of 10mm minÿ1. Hardness was reported.

RESULTS AND DISCUSSIONAmylose content, solubility and swelling propertiesRelatively wide variation was observed in the amylose

content of the different genotypes with values ranging

from 20.1% to 35.1% (Table 1). High values were

exhibited by Russet Burbank, Van Gogh and Granola.

Some genotypes had higher amylose contents than

previously reported by Wiesenborn et al9 who used the

same method of analysis. The higher values could be

attributed to differences in starch extraction and

variation in growing conditions.

The variety Norchip had the highest swelling

volume (Table 1) while the TPS hybrid, Serrana �LT-7 had the lowest. The variation among the

genotypes, however, was quite low. The results of

the solubility test (Table 1) showed a similar pattern

among the genotypes with very little variation (SD of

�2.01). The variety Bimonda had the lowest solubility

while the highest value was observed in TPS hybrid

HPS II/67 and the clone 385130.8. Correlation

analysis showed that amylose was signi®cantly corre-

lated with swelling volume but not with solubility

(Table 2). On the other hand, solubility was negatively

correlated with setback and stability ratios and

positively correlated with peak values of the RVA test.

Thermal propertiesEvaluation of thermal properties (Table 1) showed

that variation in To was very slight; with TPS hybrid

HPS 7/67 and the variety Norchip having the highest

and the lowest values, respectively. However, a fairly

substantial range in Tp values from 65.4°C to 71.8°C,

and Tc from 69.6°C to 83.1°C was found. Bimonda

and Van Gogh (Set A) and Ser. � LT-7 and HPS 7/67

(Set C) had Tp above 70°C. The variety Bimonda had

the highest Tc while varieties Granchip and Itasca had

the lowest. Reasons for variation in gelatinization

temperatures include variation in degree of crystal-

linity which imparts structural stability,10 or a more

stable amorphous region or variation in degree of

chain branching.11 High gelatinization enthalpy values

were observed in the genotypes Columbus and HPS

11/67. Gelatinization enthalpy may be high when the

granular structure is more stable because of greater

crystallinity.11

Pasting characteristicsStarch pasting characteristics (Table 3, Fig 1) showed

a wide range among genotypes in distilled water, with

peak viscosity values ranging from 253 to 752,

although only 7.4% starch was used. It is well known

that unmodi®ed potato starch has an exceptionally

high cooked viscosity per dry weight of starch; partly

attributed to its high content of starch phosphate

esters. Gelatinized starch granules however, are readily

disrupted by shear during conveying and mixing

operations, resulting in greatly reduced viscosity.9

(Wiesenborn et al. 1994). There was a rapid increase

of viscosity to the peak viscosity after the onset of

Figure 1. Representative Rapid Visco-Analyzer pasting profiles of74g litreÿ1 potato starch in water for four genotypes (in order of decreasingpeak viscosity, TPS A, 385130.8, Baraka, and Diamant). Pastingparameters of Peak, HPV and CPV are indicated.

1644 J Sci Food Agric 79:1642±1646 (1999)

ZN Ganga, H Corke

pasting for most of the genotypes tested. Similar

results were obtained by Kim et al6 in their evaluation

of potato starch. The highest pasting peak values were

exhibited by two TPS hybrids, Serrana x LT-7 and

HPS II/67 and the clone B71-240.2. Some of the

European (Set A) and US (Set B) varieties which were

bred for processing either for chipping and/or fries had

also exhibited high peak values. Genotypic differences

contributed to the wide variation in paste characteris-

tics of the 24 entries.

Higher viscosity was generally observed using

distilled water, but this was signi®cantly decreased to

a more uniform value (ie more stable pasting curve)

using 10g litreÿ1 NaCl solution (Table 3). The pasting

peak values in salt solution ranged from only 192 to

239, much lower than the values observed in distilled

water. Potato starch is highly affected by electro-

lytes.2,12±14 Pasting viscosity is higher in distilled water

than in hard water containing calcium salts or in saline

solution. Muhrbeck and Eliasson15 reported that the

Table 2. Correlation coefficients forphysical parameters of potato starchdata (pasting parameters in water)

CPV HPV Peak

Stability

ratio Amylose Solubility Swelling

CPV 1.00

HPV 0.68*Peak ÿ0.44* ÿ0.19

Stability ratio 0.64* 0.46* ÿ0.92*Amylose ÿ0.17 ÿ0.34 0.12 ÿ0.26

Solubility ÿ0.01 ÿ0.16 0.51* ÿ0.54* 0.40

Swelling ÿ0.29 ÿ0.48* ÿ0.07 ÿ0.16 0.41* 0.11

To 0.23 0.36 0.07 0.16 ÿ0.34 ÿ0.18 ÿ0.66*Tp 0.06 0.16 0.22 ÿ0.05 ÿ0.24 0.02 ÿ0.67*Tc 0.21 0.21 ÿ0.12 0.29 ÿ0.36 ÿ0.21 ÿ0.54*DH ÿ0.20 ÿ0.32 0.07 ÿ0.08 ÿ0.24 ÿ0.17 ÿ0.05

* Signi®cant at p<0.05; n =24.

Table 3. Pasting parameters and gel hardness in water, and pasting parameters in 10g litreÿ1 NaCl of 24 potato genotypes

Genotype In distilled water In 10g litreÿ1 NaCl

Peak HPV CPV Stability ratio Hardness Peak HPV CPV Stability ratio

Set A

Baraka 425 227 253 0.53 60.9 271 199 233 0.73

Bimonda 301 266 241 0.88 37.0 208 176 223 0.84

Columbus 390 219 249 0.56 64.2 200 167 254 0.83

Diamant 275 218 288 0.79 62.1 195 168 276 0.86

Donald 253 212 281 0.84 57.0 198 159 223 0.80

Hertha 338 261 324 0.77 60.7 197 176 257 0.89

Remarka 368 299 341 0.81 61.4 192 178 292 0.92

Serenade 306 267 352 0.87 66.4 197 170 278 0.86

Signal 392 241 272 0.62 38.2 213 183 258 0.86

Van Gogh 295 246 358 0.83 35.0 186 157 249 0.84

Set B

Russet Burbank 478 229 258 0.48 47.9 235 173 237 0.74

Chipetah 268 222 283 0.83 35.6 228 172 244 0.75

Granchip 583 219 243 0.38 44.3 234 177 232 0.76

Itasca 459 235 260 0.51 36.9 217 177 256 0.82

Norchip 519 222 252 0.43 49.9 198 164 251 0.83

Shepody 585 222 245 0.38 38.3 219 179 258 0.82

Set C

B71-240.2 637 215 240 0.34 36.0 218 175 232 0.80

I-1035 401 196 228 0.49 34.2 239 170 215 0.71

TPS A 752 229 262 0.31 35.6 198 162 272 0.82

TPS B 352 222 261 0.63 39.0 201 167 255 0.83

TPS C 636 221 253 0.35 38.3 213 184 256 0.86

385130.8 574 270 298 0.47 36.0 218 181 271 0.83

LBR 1±5 365 233 267 0.64 48.2 222 187 266 0.84

Granola 372 228 261 0.61 40.9 209 179 253 0.86

Mean 423 235 80 0.61 46.0 212 173 253 0.82

SD 136 24 39 0.19 11.3 19 10 19 0.49

J Sci Food Agric 79:1642±1646 (1999) 1645

Quality of potato starch

reduction in swelling volume with sodium chloride

explains the large reduction in the dynamic viscosity of

potato starch pastes on addition of low levels of

electrolytes. The effects of 0.1g litreÿ1 sodium chlor-

ide and 0.1g litreÿ1 sulphite on the swelling and

solubility of potato starch were similar.16 Different

genotypes varied in their reactions to NaCl, eg the

TPS hybrid Serrana � Lt-7 which had unusually high

peak viscosity of 752 in distilled water was greatly

reduced to 198 with the use of 10g litreÿ1 NaCl

solution while in the variety Chipetah, very little effect

was observed with its peak value of 268 in distilled

water reduced to 228 (Table 3). The change on CPV

value was not so dramatic except for some Dutch

varieties (Set A) like Donald, Hertha, Remarka,

Serenade and Van Gogh which had decreased CPV

in 10g litreÿ1 NaCl solution. Likewise the HPV values

were signi®cantly reduced with the use of 10g litreÿ1

NaCl solution in varieties Baraka, Bimonda, Hertha,

Remarka and Serenade. The stability ratio followed

the same pattern with most of the genotypes exhibiting

higher values in 10g litreÿ1 NaCl.

Gel hardnessThe hardness of the gel formed by the starch after

pasting varied by genotypes (Table 3). The Set A or

the Dutch varieties showed more variability than the

rest of the entries. The highest value was observed in

the genotype Serenade while varieties Bimonda, Signal

and Van Gogh had low values. Variation within the

other two sets (B and C) of genotypes was less. Set C

genotypes, which are mostly table-type potatoes, had

lower values.

CONCLUSIONKnowledge of the starch viscosity characteristics of

incoming raw material is important in industrial potato

processing for several reasons. Monitoring and control

of incoming raw material enables appropriate deter-

mination of suitability for particular uses. It enables

selection of suitable varieties for speci®c end-uses, and

more informed speci®cations in contracting with

farmers for supply of material. The impact of proces-

sing variables (such as variation in water quality which

may impart signi®cant differences in viscosity beha-

vior) can also be assessed. We have shown that wide

variation exists in starch properties of Philippine-

adapted potato genotypes. Breeders and processors

should consider these differences in formulating

strategies for the future development of the crop.

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